1. Field of the Invention
This invention relates to the production of polymerizable compositions comprising the reaction product of an acrylic monomer such as acrylic or methacrylic acid or their anhydrides or acid chlorides, with an oxyalkylated allyl alcohol, such as an ethoxylated or propoxylated allyl alcohol, each having a relatively low degree of oxyalkylation, which compositions are useful as radiation-crosslinkable diluents for radiation-hardenable compositions.
2. Description of the Prior Art
Radiation-hardenable coating compositions are well known in the art. Monomers typically used heretofore for such purpose include acrylic acid esters of 1,6-hexane diol, diethylene glycol, 1,4-butanediol, trimethylolpropane, pentaerythritol or glycerol. Polyethylene and triethylene glycol diacrylates are disclosed as constituents in photopolymerizable compositions, for example, in U.S. Pat. Nos. 2,951,758 and 3,060,023 and neopentyl glycol acrylate compositions are disclosed for bonding metals in U.S. Pat. No. 3,125,480.
The nature and proportion of these comonomeric acrylic acid esters in binders (oligomers) may influence the chemical and physical properties of the resultant hardened films, for example, reactivity, viscosity, hardness, adhesion, and elasticity. In this connection, it is known, for example, that hexanediol-bis-acrylate effectively reduces the viscosity of a resin, but at the same time exhibits an adverse effect upon the reactivity of the binder. In contradistinction, it has been reported that trimethylolpropane triacrylate has only a slight effect upon the reactivity of the binder, but it is unable sufficiently to reduce the viscosity, and at the same time, imparts greater hardness but also poor adhesion to the film on account of the relatively high cross-linking density. Furthermore, it is known that monomer diluents containing the allyl group, including, for example, allyl acrylate and allyl methacrylate, exhibit strong, pungent disagreeable odors, are lachrimatory, and are severe skin irritants, thereby limiting their practical use in binder formulations.
Photopolymerizable compositions comprising a thermoplastic macromolecular organic polymer binder, an addition polymerizable branched chain polyol polyester of an alphamethylene carboxylic acid of 3-4 carbon atoms, e.g. polyoxyethyltrimethanolpropane triacrylate or trimethyacrylate and polyethylpentaerythritol tetraacrylate or tetramethyacrylate, having average molecular weights of at least about 450 and an addition polymerization initiator activable by actinic radiation are described in U.S. Pat. No. 3,380,831. The presence of the ether group as a repeating unit in the additive polymerizable compounds renders these monomers hydrophilic and less soluble in oils, which in turn reduces skin diffusion resulting in lower toxicity. It is also known, from U.S. Pat. No. 3,368,900, that triacrylates are capable of production from reaction products of trimethylolpropane and up to about 20 moles of ethylene oxide, which are useful for photopolymerization reactions.
More recently, radiation-cross linkable diluents consisting of a mixture of triacrylates of a reaction product of trimethylolpropane and ethylene oxide with an average degree of ethoxylation of from 2.5 to 4, and having a particular product disribution have been disclosed in U.S. Pat. No. 4,180,474. However, it is also known, for example, from U.S. Pat. No. 4,088,498 that compounds free from ether linkages are preferred for such purpose.